Packing material



July 23, 1968 c. E. DODGE, JR 3,393,504

PACKING MATERIAL Filed Feb. 8, 1966 INVENTOR. Ct EVE'LAND 5. 00065112 AT TMNEYS.

United States Patent 01 hoe 3,393,504 Patented July 23, 1968 3,393,504PACKENG MATERIAL Cleveland E. Dodge, J12, Hoosick Falls, N.Y., assignor,by mesne assignments, to Dodge Industries, Hoosick Falls, N.Y., acorporation of Delaware Filed Feb. 8, 1966, Ser. No. 525,951 7 Claims.(Cl. 57144) ABSTRACT OF THE DISCLGSURE A packing material having a coreformed of one or more thin polytetrafiuoroethylene tapes, the core beingoverwrapped with a tensioned tape of the same or similar material. Thepacking is suited for making gaskets, valve or stem packings and forsealing pipe threads and the like.

A packing material having a core formed of one or more thinpolytetrafiuoroethylene tapes, the core being overwrapped with atensioned tape of the same or similar material. The packing is suitedfor making gaskets, valve or stem packings and for sealing pipe threadsand the like.

This invention is an improved material for making gaskets, packingvalves and stems, for sealing pipe threads and for other like uses. Itis a continuous, strong and compressible polytetrafiuoroethylene strandcomposed of a thin outer tape wound about one or more core tapes. It ischaracterized by chemical inertness and high tensile and compressivestrength and is ideally suited for use in packing flanged or threadedconnections, valves, stems, stufiing boxes, expansion joints and thelike.

The component tapes are composed of polytetrafiuoroethylene or similarmaterials such as the copolymer of tetrafluoroethylene andhexafiuoropropylene or other copolymers of tetrafiuoroethylene and otherunsaturated organic compounds having a terminal ethylenic double bond,for example, ethylene, chlorotrifiuoroethylene or the like. The polymer,polytetrafiuoroethylene, is preferred; however, the term as hereinemployed includes within its scope the above-mentioned copolymers.

Polytetrafluoroethylene is characterized by chemical inertness toaqueous alkalies, concentrated acids, oxidizing agents and organicsolvents. In the form of thin tapes, as employed herein, the material ischaracterized by a tensile strength of about 9002500 p.s.i.longitudinally and about 50-500 p.s.i. transversely. In forming thematerial of this invention, unsintered polytetrafiuoroethylene, having aspecific gravity of about 1.42.4, may also be used.

The component tape pieces of unsintered or sinteredpolytetrafiuoroethylene may be between about 1 and 20 mils thick and0.05 and 0.75 inch wide and may be formed by extrusion. Extrusion ofunsintered polytetrafiuoroethylene of the above dimensions is describedin U.S. Patent No. 3,002,770 (issued on Oct. 3, 1961 to I. A. Chestnutet al.).

Packing materials have been made by winding a tape about a core andpacking materials in other forms have been made from sinteredpolytetrafiuoroethylene. However, my invention is distinctive andunique, in that both the outside winding and the internal core materialare formed from the same or similar thin polymeric tape, and givesunexpected properties. Single, uniform strands of, or other forms of,polytetrafiuoroethylene when used in packing tend to extrude out of thepacked joint. My improved packing material is readily formed into usefulshapes and does not extrude during service. Due to the strength of thematerial it remains in place as an efiective and improved packing orseal.

A better understanding of the preparation and use of the present packingmaterial may be had by reference to the accompanying figure whichdiagrammatically shows the preparation of a packing material of thepresent invention by winding a tape about three core tapes. Referring tothe figure, an outer tape 10 is wound about three core tapes 12, 14 and16. The core tapes are guided through a conventional wire taping machinenot shown which winds the outer tape 10 around the core tapes. Such amachine is manufactured by the Dodge Machine and Tool Company, HoosickFalls, N.Y., and designated CW 64. The core may contain one or moretapes, preferably between two and thirty. This strand, composed of theouter tape and the core tapes, may be applied to flanged or threadedconnections, valves, pump housings or the like. A number of thesestrands, for example seven, may be used to form the core of a largerstrand by winding them in the manner shown in the figure to form a corewhich is overwound with another similar tape. Such a composite strandhas usefulness in applications requiring a greater bulk of packingmaterial.

The packing material of my invention is characterized by high chemicalresistance and, .due to the method of winding a polytetrafiuoroethylenetape about a core consisting of one or more similar tapes, by unexpecteddimensional stability and strength. The material is serviceable attemperatures between about 400 F. and 600 F., and is characterizedadditionally by flexibility, high elongation and low friction.

I claim:

1. A packing material comprising at least one outer tape wound about oneor more core tapes, the tapes being composed of a material selected fromthe group consisting of polytetrafiuoroethylene and copolymers oftetrafiuoroethylene and organic compounds having a terminal ethylenicdouble bond, said tapes being characterized by a longitudinal tensilestrength of about 900-2500 p.s.i.

2. The packing material of claim 1, wherein the material ispolytetrafiuoroethylene.

3. The packing material of claim .1, wherein the material is extrudedunsintered polytetrafiuoroethylene.

4. The packing material of claim 1, wherein the tapes are between about1 and 20 mils thick and 0.05 and 0.75 inch wide.

5. The packing material of claim 1, containing between 2 and 6 coretapes and l outer tape of unsintered polytetrafluoroethylene.

6. The packing material of claim 1, wherein the extruded material is acopolymer of tetrafluoroethy-lene and hexafiuoropropylene.

7. A packing material comprising at least one outer tape ofpolytetrafiuoroethylene wound about a plurality of core strands composedof the material of claim 2.

References Cited UNITED STATES PATENTS 1,325,876 12/1919 McClure 1611752,497,046 2/1950 Kropa et al. 281 2,578,523 12/1951 Llewellyn et al.28l.4 2,764,506 9/1956 Piccard et al. 28--1 3,306,155 2/1967 Zumeta etal 871 FRANK I. COHEN, Primary Examiner.

W. A. SCHROEDER, Assistant Examiner.

